[Perl/perl5] b6ac64: embed.fnc: Don't compile undefined function

[Karl Williamson via perl5-changes]

  Branch: refs/heads/blead
  Home:   https://github.com/Perl/perl5
  Commit: b6ac642e0c634eb686764eea92af294114f806ef
      
https://github.com/Perl/perl5/commit/b6ac642e0c634eb686764eea92af294114f806ef
  Author: Karl Williamson <k...@cpan.org>
  Date:   2024-02-07 (Wed, 07 Feb 2024)

  Changed paths:
    M embed.fnc
    M embed.h
    M proto.h

  Log Message:
  -----------
  embed.fnc: Don't compile undefined function

This function now is defined only when USE_LOCALE is #defined; move its
specification in embed.fnc accordingly